In a microwave phased array system, there are multiple radio frequency channels (for example, transmit/receive channels). Each radio frequency channel has a corresponding antenna. There are one or more phase shifters on each radio frequency channel. After a specific phase is set for each phase shifter, a phase shift operation may be performed on a radio frequency signal, so as to implement beamforming. However, an effect of beamforming heavily depends on consistency of phases of the multiple radio frequency channels. For example, when a phase shift of a phase shifter is configured as 0, it is required that phase differences among signals transmitted by multiple antennas are 0. However, time delays for the signal passing through frequency mixers on all radio frequency channels are different, time delays for the signal passing through filters are different, and so on, and the phase differences among the signals transmitted by the multiple antennas are not 0. Therefore, initial phase calibration needs to be performed on each radio frequency channel.
In the prior art, as shown in FIG. 1, a transmit channel A transmits signals on multiple channels, and a receive channel B receives signals on a single channel. A digital part A generates a baseband signal, and sends the baseband signal to the transmit channel A. After converted by a digital to analog converter (DAC), the digital baseband signal becomes an analog baseband signal, and then the analog baseband signal is split into four analog baseband signals by a power splitter. After separately mixed, filtered, phase-shifted, and amplified, the four analog baseband signals are transmitted by antennas. After an antenna of the receive channel B receives signals transmitted by the transmit channel A, amplification, filtering, phase shift, and frequency mixing operations are performed on the signals, and the receive channel B obtains the received baseband signals. After sampling is performed by an analog to digital converter (ADC) on the baseband signals, the baseband signals are processed by a digital part B. The digital part B extracts an available signal, and feeds back the available signal to the digital part A by using a feedback channel. The digital part A generates initial phase calibration values of phase shifters on the multiple channels according to the fed-back signal, thereby implementing initial phase calibration of four radio frequency channels shown in FIG. 1.
However, in the prior art, the signals transmitted by the antennas of the transmit channel A can arrive at the digital part B only through the receive channel B, which causes low accuracy of the generated initial phase calibration values due to impact of channel interference.